A startup called Cruise joins Google and other car companies in the autonomous car craze. Cruise calls its self-driving car 'a highway autopilot' that controls steering and braking to ensure the drivers' safety.

If things go according to plan, autonomous vehicles will begin driving themselves into showrooms within the next year or two. They'll be limited at first, but they'll still have many of the features we've seen in fully autonomous concepts -- features like automated braking, lane assist, adaptive cruise control, and pedestrian detection.

But what about those of us who have cars we like, who don't want to shell out for a brand new, self-driving car? A startup called Cruise has begun sharing details about an aftermarket device that can achieve many of the same effects.

The first iteration of that device is the Cruise RP-1. According to the manufacturer, "The RP-1 is a highway autopilot. It controls your steering, throttle, and braking, making sure your car remains safely in its lane and a safe distance from the car in front of you."

A sensor pod that's mounted on the outside of the vehicle, just above the rearview mirror. (In promo pics, it's bolted directly to the roof, but in the video above, it's placed on a rack that runs the width of the car.) The pod is the eyes of the system, containing cameras and radar to measure the distance between you, nearby vehicles, and other hazards. Cruise hasn't given dimensions, but it looks to add about seven or eight inches of height to a vehicle when placed directly on the roof.

A computer that's mounted in the trunk. This is the brains of the system, taking the data provided by the sensor pod and translating it into actions like braking, acceleration, and so on. Cruise says that it requires "less than two feet of space".

A control button that sits on a panel between the driver's seat and the center console. This, quite simply, turns the device on and off.

Presumably there are a few wires that connect the computer to your car's steering, acceleration, and braking system, too, but you know: details.

Caveats

As exciting as an aftermarket autonomous driving system might seem, it's not for everyone -- and we mean that literally. Cost isn't the only limitation. In tiny print on the reservation page, Cruise notes that:

We can understand item #2. Practically speaking, the RP-1's control panel has to fit a specific space, meaning that Cruise will likely have to custom build panels for a range of makes and models. And from a marketing standpoint Audi is a high-end brand with many customers who can afford to shell out for the RP-1. (For what it's worth, though, Audi isn't amused.)

Given all that, item #3 makes sense. It's clearly in Cruise's best interest to have as many Audis on the road as possible.

Item #1 seems a little strange, though. Is Cruise saying that the RP-1 only works in close proximity to celebrities? Or redwoods? Or tar pits? Or is Cruise trying to say that its system is legal only in California? Because while it's true that California's DMV has been aggressive insetting rules for autonomous vehicles, it's not the only state that's working on that.

Our take

This may be the first aftermarket autonomous driving system offered to the public, but you can bet it won't be the last. Who will come out on top: aftermarket manufacturers or automakers themselves? If the infotainment wars have taught us anything, we'd bet on the former, but it's still very early in the game.

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